A cyclic power generation system and method coupling SOFC and CO2 enrichment

Abstract

The present application relates to the technical field of solid oxide fuel cell, and particularly relates to a circulating power generation system and method coupling SOFC and CO2 enrichment. The system comprises a solid oxide fuel cell, an anode gas supply unit, a cathode gas supply unit, a waste heat utilization unit, a regenerator and a CO2 enrichment unit. The waste heat utilization unit comprises a first separator, a combustion chamber, a turbine and a generator. The inlet of the first separator is connected with the outlet of the anode. Two outlets of the first separator are respectively connected with the anode gas supply unit and the inlet of the combustion chamber. The outlet of the combustion chamber is connected with the inlet of the turbine. The turbine is connected with the generator. The regenerator has a heat releasing section, a first heat absorbing section, a second heat absorbing section, a third heat absorbing section and a fourth heat absorbing section connected in sequence. The inlet of the CO2 enrichment unit is connected with the outlet of the heat releasing section. CO2 of one outlet is heated by the fourth heat absorbing section and then enters the inlet of the cathode gas supply unit. CO2 of another outlet is used for storage.

Description

Technical Field

[0001] This invention relates to the field of solid oxide fuel cell technology, and more particularly to a cyclic power generation system and method that couples SOFC and CO2 enrichment. Background Technology

[0002] A fuel cell is a power generation device that directly converts chemical energy into electrical energy through an electrochemical reaction. Among them, solid oxide fuel cells (SOFCs) operate at temperatures of 600–1000℃, have high waste heat utilization value, and can be used for combined heat and power (CHP), improving energy utilization efficiency to over 90%. Summary of the Invention

[0003] This invention provides a cyclic power generation system and method that couples SOFC and CO2 enrichment, which can effectively utilize the waste heat of high-temperature exhaust gas from solid oxide fuel cells.

[0004] In a first aspect, embodiments of the present invention provide a cyclic power generation system coupling SOFC and CO2 enrichment, comprising:

[0005] Solid oxide fuel cells, including a cathode and an anode, are used for connection to an external inverter;

[0006] An anode gas supply unit, connected to the anode, is used to supply fuel gas to the anode;

[0007] A cathode gas supply unit, connected to the cathode, is used to supply oxygen to the cathode;

[0008] The waste heat utilization unit includes a first separator, a combustion chamber, a turbine, and a generator. The inlet of the first separator is connected to the outlet of the anode. The two outlets of the first separator are respectively connected to the anode gas supply unit and the inlet of the combustion chamber. The outlet of the combustion chamber is connected to the inlet of the turbine. The turbine is connected to the generator.

[0009] The regenerator has a heat-releasing section, a first heat-absorbing section, a second heat-absorbing section, a third heat-absorbing section, and a fourth heat-absorbing section connected in sequence. The temperatures of the heat-releasing section, the first heat-absorbing section, the second heat-absorbing section, the third heat-absorbing section, and the fourth heat-absorbing section decrease sequentially. The inlet of the heat-releasing section is connected to the outlet of the turbine. The first heat-absorbing section and the third heat-absorbing section are both connected to the anode gas supply unit, and the second heat-absorbing section is connected to the cathode gas supply unit.

[0010] The CO2 enrichment unit has its inlet connected to the outlet of the exothermic section. CO2 from one outlet is heated by the fourth absorbent section and then introduced into the inlet of the cathode gas supply unit. CO2 from the other outlet is used for storage.

[0011] Secondly, embodiments of the present invention provide a cyclic power generation method coupling SOFC and CO2 enrichment, applied to the cyclic power generation system described in any of the above embodiments, comprising:

[0012] The solid oxide fuel cell is used to generate electrical energy;

[0013] Fuel gas is supplied to the anode using the anode gas supply unit;

[0014] Oxygen is supplied to the cathode using the cathode gas supply unit;

[0015] The waste heat recovery unit absorbs the exhaust heat from the solid oxide fuel cell.

[0016] The regenerator absorbs the exhaust heat from the turbine and transfers the absorbed heat to the cathode gas supply unit and the anode gas supply unit.

[0017] The CO2 enrichment unit is used to enrich a portion of the CO2 discharged from the turbine, and another portion of the CO2 discharged from the turbine is heated by the fourth heat absorption section and then introduced into the inlet of the cathode gas supply unit.

[0018] As can be seen from the above solutions, the coupled SOFC and CO2 enrichment cycle power generation system and method provided by the present invention can effectively utilize the exhaust heat of the solid oxide fuel cell to generate electricity by setting up a waste heat utilization unit; by connecting one outlet of the first separator to the anode gas supply unit, the fuel utilization rate of the solid oxide fuel cell can be improved; by setting up a regenerator, the exhaust waste heat of the turbine can be effectively utilized; by setting up a CO2 enrichment unit, carbon enrichment can be achieved, and the heat generated by the SOFC during power generation can be cooled; in addition, since the cathode gas supply unit only supplies oxygen to the cathode, impurities can be avoided from interfering with the SOFC, thereby reducing the carbon enrichment cost. Therefore, the above technical solution can effectively utilize the waste heat of the high-temperature exhaust of the solid oxide fuel cell. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic diagram of a coupled SOFC and CO2 enrichment cycle power generation system provided for an embodiment of the present invention;

[0021] Figure 2 for Figure 1 The diagram shows the condensate of the circulating power generation system in one application scenario.

[0022] Figure label:

[0023] 1-Solid oxide fuel cell;

[0024] 2- Anode gas supply unit;

[0025] 21-Water pump;

[0026] 22-First compressor;

[0027] 23 - First mixer;

[0028] 24-Pre-reformer;

[0029] 3-Cathode gas supply unit;

[0030] 31-Third compressor;

[0031] 32 - Second mixer;

[0032] 4- Waste heat utilization unit;

[0033] 41 - First separator;

[0034] 42 - Combustion chamber;

[0035] 43-Turbine;

[0036] 44 - Second compressor;

[0037] 5-Regenerator;

[0038] 6-CO2 enrichment unit;

[0039] 61-Condenser;

[0040] 62-Gas-liquid separator;

[0041] 63 - Second separator;

[0042] 64 - Fourth Compressor;

[0043] 65 - Fifth Compressor;

[0044] 66 - Storage tank. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Please see Figure 1 One embodiment of the present invention provides a cyclic power generation system coupling SOFC and CO2 enrichment, the system comprising:

[0047] Solid oxide fuel cell 1 includes a cathode and an anode for connection to an external inverter (not shown in the figure);

[0048] Anode gas supply unit 2, connected to the anode, is used to supply fuel gas to the anode;

[0049] Cathode gas supply unit 3 is connected to the cathode and is used to supply oxygen to the cathode;

[0050] Waste heat utilization unit 4 includes a first separator 41, a combustion chamber 42, a turbine 43 and a generator. The inlet of the first separator 41 is connected to the outlet of the anode. The two outlets of the first separator 41 are respectively connected to the anode gas supply unit 2 and the inlet of the combustion chamber 42. The outlet of the combustion chamber 42 is connected to the inlet of the turbine 43. The turbine 43 is connected to the generator (not shown in the figure).

[0051] The regenerator 5 has a heat release section, a first heat absorption section (i.e., section AB), a second heat absorption section (i.e., section CD), a third heat absorption section (i.e., section EF), and a fourth heat absorption section connected in sequence. The temperatures of the heat release section, the first heat absorption section, the second heat absorption section, the third heat absorption section, and the fourth heat absorption section decrease sequentially. The inlet of the heat release section is connected to the outlet of the turbine 43. The first heat absorption section and the third heat absorption section are both connected to the anode gas supply unit 2, and the second heat absorption section is connected to the cathode gas supply unit 3.

[0052] The CO2 enrichment unit 6 has its inlet connected to the outlet of the exothermic section. The CO2 from one outlet is heated by the fourth absorbent section and then fed into the inlet of the cathode gas supply unit 3. The CO2 from the other outlet is used for storage.

[0053] In this embodiment, by setting up a waste heat utilization unit 4, the exhaust heat of the solid oxide fuel cell 1 can be effectively utilized to generate electricity; by connecting one outlet of the first separator 41 to the anode gas supply unit 2, the fuel utilization rate of the solid oxide fuel cell 1 can be improved; by setting up a regenerator 5, the exhaust waste heat of the turbine 43 can be effectively utilized; by setting up a CO2 enrichment unit 6, both carbon enrichment and cooling of the heat generated by the SOFC during power generation can be achieved; in addition, since the cathode gas supply unit 3 only supplies oxygen to the cathode, impurities can be avoided from interfering with the SOFC, thereby reducing the cost of carbon enrichment. Therefore, the above technical solution can effectively utilize the waste heat of the high-temperature exhaust of the solid oxide fuel cell.

[0054] It should be noted that the inventors creatively discovered during the research and development that to achieve CO2 enrichment at low cost, the cost of denitrification could be reduced (i.e., when air is used as the oxidant in SOFC, nitrogen is an impurity gas that contributes to carbon removal). Therefore, replacing air with oxygen could be considered. However, when oxygen is used as the oxidant in SOFC, the problem of heat dissipation in the stack cannot be effectively solved. To address this, the inventors considered introducing a portion of the enriched CO2 (specifically, the portion of CO2 after steam-water separation, as described below) into the inlet of the cathode gas supply unit 3. This would both achieve carbon enrichment and cool the heat generated by the SOFC during power generation.

[0055] Furthermore, by integrating the heat release section, the first heat absorption section, the second heat absorption section, the third heat absorption section, and the fourth heat absorption section into a single regenerator 5, the former has less heat exchange loss and a more compact structure compared to separate heat exchangers, thus saving the floor space required for the circulating power generation system.

[0056] Anode gas supply unit 2 compresses and heats the fuel and feedwater introduced into the system, mixes them with recirculated anode exhaust gas, heats the mixture, and then pre-reforms it. The pre-reformed fuel gas is then fed into the anode of solid oxide fuel cell 1. Cathode gas supply unit 3 pressurizes and heats the oxygen introduced into the system and feeds it into the cathode of solid oxide fuel cell 1. Solid oxide fuel cell 1 utilizes the electrochemical reaction between the introduced fuel gas and oxygen to convert chemical energy into electrical energy, which is then output. A portion of the exhaust gas from the anode of solid oxide fuel cell 1 is sent into combustion chamber 42 for further combustion, while the remaining exhaust gas is fed into anode gas supply unit 2.

[0057] It should be noted that recirculating part of the exhaust gas from the anode (i.e., feeding it into the anode gas supply unit 2) can also adjust the water-to-carbon molar flow ratio at the SOFC inlet (water refers to the water vapor content in the hydrocarbon fuel gas, and carbon refers to the carbon content in the hydrocarbon fuel). In some embodiments, the water-to-carbon molar flow ratio at the SOFC inlet can be in the range of 2 to 3, which can effectively avoid the occurrence of carbon deposition problems in the SOFC.

[0058] In a solid oxide fuel cell 1, oxygen in the cathode gains electrons and is converted into oxygen ions, which are then transported to the anode by the electrolyte. Thereafter, they react with the fuel in the anode to form H2O and CO2. The current is generated by the movement of electrons in the external circuit of the battery, and then the DC power is converted into AC power by the inverter to generate electricity.

[0059] In one embodiment of the present invention, the anode gas supply unit 2 includes a water pump 21, a first compressor 22, a first mixer 23 and a pre-reformer 24. The water pump 21, the third heat absorption section, the first inlet of the first mixer 23, the first heat absorption section, the pre-reformer 24 and the anode are connected in sequence. The first compressor 22 is connected to the second inlet of the first mixer 23. One outlet of the first separator 41 is connected to the third inlet of the first mixer 23 through the second compressor 44.

[0060] In one embodiment of the present invention, the cathode gas supply unit 3 includes a third compressor 31 and a second mixer 32, the outlet of the third compressor 31 is connected to the first inlet of the second mixer 32, and an outlet of the CO2 enrichment unit 6 is connected to the second inlet of the second mixer 32.

[0061] The outlet of the second mixer 32, the second heat absorption section, and the cathode are connected in sequence.

[0062] In this embodiment, considering the heat absorption temperatures of oxygen, feedwater, and mixed gas, the heat absorption settings of the heat absorption sections and the specific locations of different functional units can be determined based on the temperatures of different heat absorption sections. For example, according to the heat absorption temperature requirements, the heat absorption temperature of the mixed gas is the highest, followed by the heat absorption temperature of oxygen, and the heat absorption temperature of feedwater is the lowest, thereby realizing the cascade utilization of the exhaust waste heat of turbine 43.

[0063] In one embodiment of the present invention, the CO2 enrichment unit 6 includes a condenser 61, a gas-liquid separator 62, a second separator 63, a fourth compressor 64, and a fifth compressor 65. The gas passages of the condenser 61 and the gas-liquid separator 62 are connected in sequence to the inlet of the second separator 63. The two outlets of the second separator 63 are respectively connected to the fourth compressor 64 and the fifth compressor 65. The fourth compressor 64 is connected to the fourth heat absorption section. The outlet of the fifth compressor 65 is connected to a storage tank 66 for storing CO2.

[0064] In this embodiment, since the oxidant of SOFC is oxygen (but the gas entering the cathode of SOFC is a mixture of oxygen and CO2), the exhaust gas of turbine 43 theoretically contains only carbon dioxide and water vapor. In order to achieve carbon enrichment, water vapor needs to be separated first using condenser 61 and gas-liquid separator 62. Then, by setting a second separator 63, a fourth compressor 64 and a fifth compressor 65, both carbon enrichment and cooling of the heat generated by SOFC during power generation can be achieved.

[0065] In one embodiment of the present invention, the water path of the gas-liquid separator 62 is connected to the inlet of the water pump 21. This configuration allows for the recycling of the condensate (i.e., cooling water) generated by the gas-liquid separator 62.

[0066] like Figure 2 As shown, in one embodiment of the present invention, the water path of the gas-liquid separator 62 can also be connected to... Figure 1 The downstream section of the EF section (i.e., the section with a lower temperature) can further absorb heat from the regenerator 5. For example, the downstream section of the EF section may include three heat-releasing sections with gradually decreasing temperatures connected in sequence (i.e., in... Figure 2 The text indicates three heat exchangers with progressively decreasing temperatures: "high," "medium," and "low."

[0067] exist Figure 2 In this process, pressurized condensate (e.g., condensate from a compressor) flows sequentially through the lowest-temperature exothermic section, the intermediate-temperature exothermic section, and the highest-temperature exothermic section, before entering the inlet of a mixer. There, it mixes with the exhaust gas generated in the combustion chamber 42 and then enters the turbine 43. This method increases the inlet flow rate of the working fluid in the turbine 43, thereby increasing the expansion work done by the turbine 43 and improving the power generation efficiency of the cycle power generation system.

[0068] In this embodiment, the condensate enters the lowest-temperature exothermic section, where it is preheated to near saturation temperature. The hot water exiting the lowest-temperature exothermic section then enters a medium-temperature exothermic section, where it becomes saturated steam. Finally, the saturated steam exiting the medium-temperature exothermic section enters the highest-temperature exothermic section for further heating, resulting in superheated steam at 110°C. The steam generation process is divided into preheating, evaporation, and superheating. This fully utilizes the exhaust waste heat of turbine 43, thereby reducing the inlet working fluid temperature of the downstream condensation section and decreasing the cooling water consumption during the condensation process.

[0069] It should be noted that if the heat exchange section mentioned above is only a heat release section (or heat exchanger), compared with the combination of the heat release sections of "the lowest temperature heat release section, the middle temperature heat release section and the highest temperature heat release section", the former does not have obvious preheating, evaporation and superheating processes. Therefore, the former cannot make full use of the exhaust waste heat of turbine 43.

[0070] In one embodiment of the present invention, the fuel gas includes at least one of the following: natural gas, liquefied petroleum gas, syngas, carbon monoxide, coal gas, biomass gas, and methanol.

[0071] In summary, the circulating power generation system provided by the embodiments of the present invention effectively reduces the pollution of the environment caused by the exhaust gas emissions of the power generation system, achieves the effect of energy conservation and emission reduction, and improves the power generation efficiency of the battery. Moreover, the recycling of anode exhaust gas and the full utilization of the combustion chamber improve the fuel utilization rate of the integrated system, adapt to the development trend of solid oxide fuel cell power generation systems, and have broad application prospects.

[0072] Furthermore, one embodiment of the present invention also provides a cyclic power generation method coupling SOFC and CO2 enrichment, based on a cyclic power generation system as mentioned in any of the foregoing embodiments, comprising:

[0073] Electricity is generated using a solid oxide fuel cell 1;

[0074] Fuel gas is supplied to the anode using anode gas supply unit 2;

[0075] Oxygen is supplied to the cathode using cathode gas supply unit 3;

[0076] Waste heat recovery unit 4 is used to absorb the exhaust heat from solid oxide fuel cell 1;

[0077] The heat from the exhaust gas of the turbine 43 is absorbed by the regenerator 5 and transferred to the cathode gas supply unit 3 and the anode gas supply unit 2.

[0078] A portion of the CO2 discharged from turbine 43 is enriched by CO2 enrichment unit 6, and another portion of the CO2 discharged from turbine 43 is heated by the fourth heat absorption section and then introduced into the inlet of cathode gas supply unit 3.

[0079] It should be noted that the method embodiments provided by the present invention and the system embodiments described above belong to the same inventive concept and have the same beneficial effects. The effects of the method embodiments will not be elaborated here.

[0080] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0081] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A cyclic power generation system coupling SOFC and CO2 enrichment, characterized in that, include: A solid oxide fuel cell (1) includes a cathode and an anode for connection to an external inverter; An anode gas supply unit (2) is connected to the anode and is used to supply fuel gas to the anode; A cathode gas supply unit (3) is connected to the cathode and is used to supply oxygen to the cathode; The waste heat utilization unit (4) includes a first separator (41), a combustion chamber (42), a turbine (43), and a generator. The inlet of the first separator (41) is connected to the outlet of the anode. The two outlets of the first separator (41) are respectively connected to the anode gas supply unit (2) and the inlet of the combustion chamber (42). The outlet of the combustion chamber (42) is connected to the inlet of the turbine (43). The turbine (43) is connected to the generator. The regenerator (5) has a heat release section, a first heat absorption section, a second heat absorption section, a third heat absorption section and a fourth heat absorption section connected in sequence. The temperatures of the heat release section, the first heat absorption section, the second heat absorption section, the third heat absorption section and the fourth heat absorption section decrease in sequence. The inlet of the heat release section is connected to the outlet of the turbine (43). The first heat absorption section and the third heat absorption section are both connected to the anode gas supply unit (2). The second heat absorption section is connected to the cathode gas supply unit (3). The CO2 enrichment unit (6) has an inlet connected to the outlet of the exothermic section. The CO2 from one outlet is heated by the fourth absorbent section and then introduced into the inlet of the cathode gas supply unit (3). The CO2 from the other outlet is used for storage. The CO2 enrichment unit (6) includes a condenser (61), a gas-liquid separator (62), a second separator (63), a fourth compressor (64), and a fifth compressor (65). The gas passages of the condenser (61) and the gas-liquid separator (62) are connected in sequence to the inlet of the second separator (63). The two outlets of the second separator (63) are connected to the fourth compressor (64) and the fifth compressor (65) respectively. The fourth compressor (64) is connected to the fourth heat absorption section. The outlet of the fifth compressor (65) is connected to a storage tank (66) for storing CO2.

2. The circulating power generation system according to claim 1, characterized in that, The anode gas supply unit (2) includes a water pump (21), a first compressor (22), a first mixer (23), and a pre-reformer (24). The water pump (21), the third heat absorption section, the first inlet of the first mixer (23), the first heat absorption section, the pre-reformer (24), and the anode are connected in sequence. The first compressor (22) is connected to the second inlet of the first mixer (23). One outlet of the first separator (41) is connected to the third inlet of the first mixer (23) through the second compressor (44).

3. The circulating power generation system according to claim 2, characterized in that, The cathode gas supply unit (3) includes a third compressor (31) and a second mixer (32). The outlet of the third compressor (31) is connected to the first inlet of the second mixer (32), and one outlet of the CO2 enrichment unit (6) is connected to the second inlet of the second mixer (32). The outlet of the second mixer (32), the second heat absorption section and the cathode are connected in sequence.

4. The circulating power generation system according to claim 3, characterized in that, The water path of the gas-liquid separator (62) is connected to the inlet of the water pump (21).

5. The circulating power generation system according to any one of claims 1-4, characterized in that, The fuel gas includes at least one of the following: natural gas, liquefied petroleum gas, syngas, carbon monoxide, coal gas, biomass gas, and methanol.

6. A cyclic power generation method coupling SOFC and CO2 enrichment, characterized in that, The cyclic power generation system based on any one of claims 1-5 includes: Electricity is generated using the solid oxide fuel cell (1); Fuel gas is supplied to the anode using the anode gas supply unit (2); Oxygen is supplied to the cathode using the cathode gas supply unit (3); The waste heat utilization unit (4) absorbs the exhaust heat of the solid oxide fuel cell (1); The heat from the exhaust gas of the turbine (43) is absorbed by the regenerator (5), and the absorbed heat is transferred to the cathode gas supply unit (3) and the anode gas supply unit (2). The CO2 enrichment unit (6) is used to enrich a portion of the CO2 discharged from the turbine (43), and another portion of the CO2 discharged from the turbine (43) is heated by the fourth heat absorption section and then introduced into the inlet of the cathode gas supply unit (3).

Images